Making the cut: Researchers use cacao DNA to test for premium chocolate

There might finally be a way to tell if that box of La Maison du Chocolat you bought your sweetheart for Valentine’s Day was worth the $200.

Cacao beans are the source of cocoa, the primary ingredient used to make chocolate. Premium chocolate is set apart from ordinary chocolate by its standard of production and sourcing.

But cacao beans of lower quality regularly find their way into even the most luxurious premium chocolates, many of which carry a hefty  price tag.

That’s why a team of researchers have come up with a way to authenticate premium chocolate by assessing the purity of cacao beans using genomics.

The study, published earlier this month in the American Chemical Society’s Journal of Agricultural and Food Chemistry, was led by Dr. Dapeng Zhang and Dr. Lyndel Meinhardt of the United States Department of Agriculture.

“We’re not going to tell you if different kinds of cacao beans are any better or any worse from each other,” said Dr. Meinhardt.

“This is a method to authenticate what are premium types that are already known by the chocolate industry.”

Dr. Meinhardt said the discovery was an offshoot of a larger study the team has been working on for several years, exploring the genetic diversity of the theobroma cacao, the plant where cocoa beans come from.

Because the plants are native to South America, his team was having difficulties getting leaf samples sent from half way around the world in order to do DNA analyses. This led them to try and develop a new method  to carry out their tests without acquiring a new sample every time.

“There were a couple of leading causes that kind of led us down this road, but I think the primary one was just wanting to try to develop a new tool that we could use,” Dr. Meinhardt said.

How it works

The team designed the method by successfully identifying unique DNA markers called single-nucleotide polymorphism, or SNPs (pronounced “snips”) on cacao beans. Each individual species of cacao has a different set of SNPs.

Importantly, this method of assessing the quality of different cacao beans can be applied to large samples as well as to individual cacao beans, making it a potentially powerful tool.

“Once a panel of SNP markers ‘fingerprint’ is validated for a particular variety of cacao bean, the technique can easily be scaled up to analyze the DNA of hundreds of cacao beans in a single day,” said Dr. Shelly Hepworth, a professor in Carleton University’s department of biology specializing in plant genomics.

“This is a great application for ‘DNA fingerprinting’ in the food industry.”

While DNA-based authentication has been widely used in many different species of crops, Dr. Meinhardt and his team said this is the first time they know it has been used to authenticate cacao beans.

Dr. Meinhardt said his team’s method will do more than just verify the purity of premium chocolate. They hope it will also prevent cacao farmers from exclusively growing only the cheapest and easiest to farm beans.

“If they (cocoa farmers) are producing a premium crop, or a premium variety, there will be more assurances that the premium variety will make it to the chocolate maker and ultimately to the consumer as a premium product,” said Dr. Meinhardt.

This in turn will preserve the biodiversity of different cacao species, and ensure the source of premium chocolate will not slowly diminish.

“With DNA fingerprinting, it is now be easy to test premium beans for adulteration on a large scale and to spot suppliers who are unreliable,” Dr. Hepworth said.

“This can only be good news for chocolate producers who can now confirm that their chocolate contains only the finest ingredients.”

If this method is widely applied, more consumers who spend good money on premium chocolate can rest assured they get their money’s worth, and won’t end up paying for chocolate adulterated with low quality cacao.